Commentators believe the two biggest problems facing the US president are the economy and what to do about the threat of Iran.

The President will soon have to take action on the looming US "fiscal cliff" - a cocktail of tough spending cuts and tax increases that will come into effect on January 1 if American politicians fail to reach a deal on its budget.

Mr Obama will have to try to push for a deal with the Republicans as soon as possible to avoid this outcome.

Iain Duncan Smith, the Work and Pensions Secretary, has warned the fiscal cliff could have an even "bigger" impact on than the UK than the eurozone crisis.

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"I think the reality for all of us... is that the US is a massive and important feature because we do a huge amount of a proportion of our trade with America," he said over the weekend.

"Also, we are the biggest single investor in the United States by a long way. America is important to us, its vitally important to global trade, and the fact that it hasn't bounced back from this recession... makes a very worrying picture indeed, with unemployment historically high in the United States, and really not a lot of serious new economic activity."

Others said world leaders are likely to "prefer" President Obama to Mitt Romney as he is already aware of the background and dangers of Iran.

Sir Malcolm Rifkind, MP for Kensington and a former Defence Secretary, said President Obama will also have to deal with trouble in the Middle East within months.

He said it would have been "unfortunate" to put the decision on what to do about Iran "on the desk of a new president"

"The immediate crisis will now be what happens with Iraq and nuclear weapons," he told the BBC Radio 4 Today programme.

“I think that is the single most important reason why the international world will probably prefer Obama to continue. Romney would have been a pretty moderate president but he has no background experience on foreign policy.

"When you think of some of the crucial decisions the president’s going to have to make, particularly in the next few months on Iran and whether some sort of military response to Iran is going to come from the United States, to put that on the desk of the new president, he wouldn’t necessary have come to the wrong decision but it would be much more unfortunate if there wasn't an alternative available, which there is.”